This invention relates to an optical document scanning system for a document reproduction machine and, more particularly, to an improved assembly for supporting the optical components used during the document scan operation.
In the document reproduction art, an original document to be reproduced is typically placed on a stationary platen and illuminated by a incremental line-scanning optical system. Reflected light rays from the document travel along an optical path and are projected by a lens on to a photosensitive image member. The latent image of the document formed on the image member is then developed by appropriate marking material, and the developed image transferred to a record medium such as paper. Various types of scan mechanisms are known in the art, but the most widely used utilize a pair of guide rails which are mounted in a parallel plane beneath the document platen. The scanning components are mounted on one or more movable scan carriages which are driven by a cable arrangement to run back and forth beneath the platen and supported by the guide rails. Examples of such prior art scan systems employing an elongated illuminated lamp and scan mirrors to scan/illuminate the document are shown in U.S. Pat. Nos. 4,367,945, 4,155,641 and 4,603,963. The document to be reproduced may also be scanned by a raster input scanner (RIS), typically a CCD sensor array. The RIS type scanner is supported for movement beneath the document platen and is moved in the scan, re-scan direction by a scan assembly basically similar to the ones used in the above-identified patents. U.S. Pat. No. 4,500,197 discloses a RIS type scan system. The prior art scanning system can be characterized as being secured to, and supported by, the sides of a frame assembly. Thus, U.S. Pat. No. 4,367,945 to Abe discloses a scanning support structure for an electrostatic copying machine comprising a guide rail 22 and a guide rod 23 which together support and absorb the loads of two movable carriages 12 and 14, while being supported by frame members 20 and 21. U.S. Pat. No. 4,155,641 to Sagara et al. discloses a scanning apparatus comprising three parallel guide rods 52, 53, and 54, attached to a beam member 20, which support the loads imposed by two movable optical scanning carriages 50 and 51. U.S. Pat. Nos. 4,603,963 to Hinton et al., and 4,710,017 to Watanabe et al. are references which disclose scanning systems comprising a pair of frame supported parallel guiding members which absorb the shock and loads of a moving carriage apparatus within an electrostatic copying machine. U.S. Pat. No. 4,500,197 to Dannatt discloses a support structure for a flat bed scanner comprising a pair of parallel, elongated guide rods 55 and 62 fixed to left and right end plates 14 and 16, which form rigid support for the loads imposed by a movable RIS optical scanning carriage assembly 12.